1. Field of the Invention
The present invention relates primarily to a device for maintaining air circulation space proximate to thermal insulation. Particularly, the present invention is directed to a device to maintain ventilation space above thermal insulation in order to expel heat and moisture from the insulation.
2. Description of Related Art
Thermal insulation is required to reduce the energy loss from structures for the purposes of maintaining comfortable interior spaces both in heating months and cooling months. The need to reduce the consumption of fossil fuels and the “greenhouse effect” has required the ever-increasing improvement in insulation values. Dimensional lumber sizes used in the framing of structures, and standard dimensions of light steel framing members have not changed significantly in many years. The depth of framing members and therefore the insulation cavity are determined by structural requirements which, for the foregoing reason, have remained fairly constant. Exterior wall, floor and roof construction is where thermal insulation is most commonly used. The ever-increasing thickness requirements for fibrous insulation, which is the most commonly-used and economical insulation type for insulating framing cavities, makes adequate ventilation of this insulation more difficult to achieve. Increased thickness of other types of insulation, such as rigid foams and the like, also present ventilation problems, particularly if the foam is porous to any degree.
Insulation used in roofs has the most crucial requirement for ventilation over the top of the insulating materials. Roofs are required to have the greatest amount of thermal insulation, since as heat rises to the highest point of a space, it creates the highest differential between inside and outside temperatures of any part of the so-called “thermal envelope” and therefore is the area of the greatest heat loss during the heating season. During the cooling season, heat from the sun heats the roof to such an extent that it becomes the greatest source of heat gain. Use of dark-colored roofing materials only worsens the problem. In the heating and cooling seasons, insulation absorbs heat in the daytime as part of the insulation cycle. That heat must be expelled during the cooler night time hours to be ready to store new heat during the next daylight period, which helps slow down heat transfer through the insulation and into the structure. If ventilation is inadequate, or non-existent, the heat will not be expelled from the insulation and the effectiveness of the system will be reduced. However, as the heat is expelled during the night and cools down, the insulation absorbs moisture, because the cool night air is usually relatively damp. Ventilation during daylight hours expels the moisture as the insulation is heated. If ventilation is not adequate, insulation can become completely saturated with moisture and ruin drywall, plaster and ceiling finishes, causing interior dripping and risking collapse of the ceiling. Prolonged and/or frequent water retention can also promote mildew, mold and rotting of the roof structure. In today's era of more “efficient” building technology with fewer places for air to penetrate to ventilate insulation, wet insulation and the aforementioned mildew and mold problems can become very serious, often affecting the health of occupants exposed to the mold. If mold is present in large quantities, it is sometimes referred to as “sick building syndrome.”
For similar reasons, wall systems may require ventilation. Vapor barriers are often installed under drywall; or insulation batting is provided with an impermeable plastic or foil layer. However, if any part of the system is faulty, is improperly installed or becomes damaged, moisture can penetrate into the insulation and reduce its effectiveness and/or cause any of the aforementioned problems such as mold. Water and moisture can also penetrate insulation from the outside if external sheathing or siding is faulty. Accordingly, proper ventilation of the insulation within wall cavities can be crucial.
A variety of methods, systems and products have been developed for attempting to maintain a ventilation space proximate to thermal insulation. However, such conventional methods and systems suffer from certain significant deficiencies.
Before legislation brought about insulation requirements for roofs, floors and exterior walls, the ventilation cavity between the top of insulation (e.g., fibrous insulation) and sheathing was formed by simply having an insulation thickness less than the void depth.
As environmental concerns brought about the creation of energy construction codes, and these codes started to require greater thicknesses of insulation, it became necessary for the insulation to be installed carefully. The practice of “patting-down” the top of the insulation during installation came about and was initially sufficient. As the thicknesses of insulation continued to increase, the Rafter-Vent® product was developed. U.S. Pat. Nos. 4,125,971, 4,406,095, 5,341,612 and 5,600,928 are examples of such existing technology. Other patents such as U.S. Pat. Nos. 4,102,092, 4,214,510, 4,446,661 and 4,660,463 disclose devices concerned with maintaining ventilation over insulation at the eaves only, but do not maintain ventilation spaces over the entire length of the rafters.
The problems with the Rafter-Vent® and similar products are significant. FIGS. 6 and 7 illustrate this prior art product. FIG. 6 shows the Rafter-Vent® product used in a first orientation. When the Rafter-Vent® product is positioned as depicted, the insulation can still fluff between the contact points and block most of the airflow. Nevertheless, it still provides some ventilation to the insulation. FIG. 7 shows the Rafter-Vent® product used in a second, inverted orientation generally recommended by the manufacturer for eave venting. The bottom of the “U”-shaped cross section is against the insulation. Because the bottom surface of the “U” is a solid, relatively imperforate surface, it almost completely seals-off the insulation from the ventilation space. Additionally, because the most popularly used versions of Rafter-Vent products are made of approximately ⅜″ thick styrene foam plastic, it also blocks the escape of heat via conduction from the insulation because the Rafter-Vent product itself is an insulating material. An additional drawback to the Rafter-Vent product is that it is supplied to a construction site in a nested bundle. Frequently, it is delivered along with the lumber in eight foot long bundles. Because it is fragile, very light in weight, and easily broken, and usually sits on the construction site for a long period of time before it is used, construction sites are often littered with pieces of this product. Once the bundle is opened and not carefully stored, wind can pick up the large, extremely light panels and scatter them causing litter on construction sites and the neighborhoods surrounding them.
FIG. 6 is a sectional view through several bays of roof structure and insulation illustrating use of the Rafter-Vent product in a first orientation that would provide limited possibility for maintaining ventilation to the insulation material 16. However, as is evident from FIG. 6, tightly packed insulation can still force itself into the form of the Rafter-Vent product and block ventilation.
FIG. 7 is a sectional view through several bays of roof structure and insulation illustrating the use of the Rafter-Vent product in a second orientation by installing it as recommended for eave vents. As is evident from FIG. 7, most of the insulation's surface area is sealed-off from the ventilation space by the Rafter-Vent product, as noted above, because the Rafter-Vent product is made from foam plastic, which is itself an insulator, and it effectively prevents the expulsion of built-up heat from the fibrous insulation mass. Reference numeral 15 indicates the roof sheathing, reference numeral 18 indicates the fibrous insulation mass, and reference numeral 21 indicates a typical rafter in a “cathedral” ceiling, “tray” ceiling or flat roof assembly or attic joists with storage floor boards attached.
The Rafter-Vent product thus has significant deficiencies because it does not insure a uniform ventilation space and because versions of it are frequently used incorrectly (i.e., “upside-down”) rendering it ineffective for the purpose intended.
As briefly mentioned above, the method used prior to the advent of the Rafter-Vent product to form the air space was the action of the insulation installer patting the insulation down with his hand. This earlier method was, to some extent, superior to the Rafter-Vent concept since airflow was not essentially completely blocked by an impermeable foam plastic layer. However, with increased thicknesses of insulation required, the “patting down” method does not work today, because it is necessary to resist the force of the compressed insulation in order to maintain the ventilation space.
Thus, as is evident from the related art, conventional methods are ineffective for maintaining an insulation space that permits adequate ventilation of insulation material.
There thus remains a serious need for an efficient, simple and economic method and system for maintaining an insulation space proximate to thermal or acoustic insulation material in a building.